Oh I feel your pain!
DD2 was the same. Here it started with DD1 dropping her day sleep a few days after DD2 was born, then DD2 decided that she didnt need the sleep either and so she would cat nap by accident all day long. In the end I would take them for drives or walks that were long enough that either one or both of them would sleep. I didnt really care if DD1 slept or not, but I always did a happy dance when DD2 went down for a sleep.
The naps returned but not until DD2 was well over 1yr. Now she will tell me when she is tired and needs a sleep, which is most days.